Oxidative stress, in particular the oxidation of proteins, has been implicated in the phenomenon of aging, acute damage of proteins, and many chronic diseases. It is the goal of this research to investigate the basis of aging and other physiological processes by examining the molecular responses to oxidative stress. An early theory of aging was proposed by Denham Harman in 1956. It was suggested that the accumulation of free radical damaged biomolecules increased during the process of aging. Similarly, oxidative injury of proteins may be accelerated by external stressors which result in decreased protein function, protein turnover, and pathologic conditions such as ischemia- reperfusion. More specifically, on going studies combine the disciplines of organic and biological chemistry and molecular and cellular biology to investigate the causes and implications of these oxidation reactions. A number of questions concerning acute oxidative damage are of particular interest. The recent discovery of 2-oxo-histidine in oxidatively inactivated glutamine synthetase (R. Levine and colleagues) and superoxide dismutase (K. Uchida and co-workers) provide insights in to the oxidative damage of proteins. Synthesis of 2-oxo-histidine using oxygen, copper, and ascorbate as a hydroxyl radical generating system was just accomplished in the laboratory following published methods. While 2-oxo-histidine is currently being characterized, the use of this compound is highly anticipated in the development of an analytical method used to identify oxo-histidine in biological systems. The potential to screen large numbers of proteins or cultures for oxidative modification is envisioned through both high performance liquid chromatography (HPLC) and western analysis. Concurrently, emphasis is placed on characterizing the events which occur during oxidative stress of endothelial cells in tissue culture, especially the fate of glutathione. Earlier studies by Henry Ciolino demonstrated a rapid loss of energy stores within the cells and carbonyl formation. Studies have already been completed on optimizing the detection of glutathione in biological systems.